Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the zoom lens. For example, the present invention is suitable for an image pickup apparatus, such as a digital still camera, a video camera, a monitoring camera, or a broadcasting camera, that includes an image pickup element or suitable for an image pickup apparatus, such as a camera in which a silver-halide photography film is used.
Description of the Related Art
In recent years, an image pickup apparatus, such as a monitoring camera or a video camera, that includes a solid-state image pickup element has had improved functionality, and the overall size of the apparatus has been reduced. There is a demand that a zoom lens used in such an apparatus be small and have good optical characteristics. There is also a demand for a zoom lens having a high zoom ratio in order to enable imaging of a broader range with a single image pickup apparatus.
In order to meet such demands, a zoom lens that includes lens units having positive, negative, and positive refractive powers that are arranged in order from an object side to an image side is known.
Japanese Patent Laid-Open No. 2005-55625 discloses a zoom lens that has achieved a higher power while reducing distortion aberration or astigmatism by disposing a negative lens having a high refractive power in a second lens unit on a side closest to the object side.
However, in the zoom lens disclosed in Japanese Patent Laid-Open No. 2005-55625, the magnification varying burden of a third lens unit is relatively small, and thus it is difficult to achieve a high power at a sufficient level.